Preparation of stable, concentrated koh slurries



Jan. 26, 1960 J. HAPPEI. ET AL PREPARATIGN OF STABLE, CONCENTRATED KOHSLURRIES Filed Aug. l1, 1955 Inventors John Happel Charles J. Marsel i si1 2,922,755 Patented Jan. 26, 1960 PREPARATIN F STABLE, CONCENTRATED KHSL E John Happel, Yonkers, and Charles l. Mai-sel, New York, N.Y.

This invention is concerned generally with a continuous and commerciallypractical process for the production of acetylenic hydrocarbons by aseries of interrelated and coacting steps, and more speciiically, with aparticularly useful method for the manufacture of2-methyl-1,5hexadiene-Z-yne.

It has been previously known to produce various hydrocarbons havingunsaturated bonds, including both double and triple bonds, by thermalpyrolysis. This drastic technique is only applicable to the lesscomplicated types of hydrocarbon structures. For instance, methylacetylene has previously been made by the thermal pyrolysis method, butonly in relatively low yields. However, it is substantially impossibleto produce complicated molecular structures having a multiplicity ofdouble and triple bonds by this method.

Organic compounds having both acetylenic bonds and olenic double bondsgive especial difficulty in their production even on laboratory andsmall batch type operations. Various ditiiculties are encountered in theapplication of the known methods, including the degradation anddecomposition reactions ofboth the starting materials as well as theacetylenic olefin hydrocarbon products. Such byproducts and sidereactions result in both loss in yield of product as well as loss of therelatively expensive starting material.

The present invention is concerned with improved means for producingacetylenic alcohols and includes improvements in addition to thosedescribed in copending application U.S. Serial No. 384,846, tiledOctober 8, 1953, now abandoned, of which the instant application is acontinuation-in-part. This invention is more particularly concerned withthe production of the acetylenic alcohols and employs valuableimprovements in the condensation step ybetween the acetylenichydrocarbon with the carbonyl compound.

Certain of the organic compounds of the class of th alkyl-olenicacetylenes, especially 2-methyl-l,5-hexadiene-B-yne, may be prepared bythe process of this invention. This class of compounds contains both theacetylenic bond and multiple oleiinic bonds, and consequently gives theabove described diiiiculties in their preparation by previously knownmethods.

ln general, the invention involves a method for synthesizing acetylenichydrocarbons by the combination of carbonyl compounds which may beeither aldehydes or ketones with either acetylene or acetylenichydrocarbons in which caustic alkali is the most frequently usedcatalyst. The acetylenic alcohol produced as a result of this reactioncan, if desired, thereafter be converted to an acetylenic olenhydrocarbon by a dehydration. The whoie series of steps is carried outin a practical manner on a continuous scale without the usual hazardswhich are often encountered in this type of operation.

Although in the previous art, the use of suspensions of solid potassiumhydroxide has been generally disclosed, it has been found that thepreparation of such suspensions in a stable, usable, form involvesconsiderable difliculty and embraces novel features not previously knownor disclosed. Although simple suspensions may be reasonably satisfactorywhen the condensation reaction is conducted in an agitated batch vessel,they give completely unsatisfactory results when they are of necessity,made up at a period of time previous to the reaction, and then used asfeed to a continuous reactor.

Many techniques were attempted in an effort to prepare stable potassiumhydroxide suspensions and particularly using xylene as the suspensionliquid. For instance, attempts were made using liquids other thanxylene. These included alkyl acetals and polyethers. The use of Carbitol(diethylene glycol monoethyl ether) was studied. Dibutyl acetal was alsoemployed without success in attempts to prepare stable suspensions.Further, attempts were made also to employ Various so-calledsolubilizers such as mercaptans and phenols in preparing aqueoussolutions containing a high percentage of potassium' hydroxide. Anothertechnique studied was that molten potassium hydroxide was sprayed intothe reaction chamber and as the hydroxide particles solidied, a tinesuspension was obtained. The use of alcoholates was also investigated.Generally, difficulties are encountered in the preparation of thealcoholates -or acetal. The alcoholates were made by reacting potassiummetal `with the appropriate alcohol. An attempt was also made to producethe alcoholates by reacting the alcohol with potassium hydroxide, andthereafter removing the Water of reaction by distillation. This reactionwas successful only with cresol, but this reagent did not producecondensation. None of the above schemes and methods were successful foruse in continuous processes in which this reagent is used.

lIt was discovered quite surprisingly that solid potassium hydroxideparticles can be suspended by the use of a relatively small proportionof certain fatty acid salts of the alkalis. Using critical conditions ofprocedure, as will be described more particularly below, this techniqueyields unexpectedly and unusually stable suspensions of solid potassiumhydroxide in hydrocarbon diluents or solvents, such as xylene and thelike.` Such suspensions s0 formed are outstandingly suited for use incontinuous processes involving the condensation reactions.

In order to determine the various materials which can be satisfactorilyused in preparing the stable slurries, a number of comparativeexperiments were made. In each instance the same procedure was employed.50 parts of xylene and 25 parts of potassium hydroxide were heatedtogether to about C. Under these conditions, 1/2 part of oleic acidproduced a stable emulsion which upon cooling resulted in a stableslurry of iinely divided potassium hydroxide suspended in xylene. Tablel below lists some of the other materials which were tested.

TABLE I Time for Agent perceptible settling, hours Oleic acid 24. Oleicacid di1ncr 3. Mixed fatty acid rosin ester 1 Less than 1. Acetate saltof a diamine 2 Do. Vinyl acetate Do. Acetone Do. CarbitoL- Do.

1. A mixed fatty acid rosin ester made by condensing 15 moles ethyleneoxide perlrnole of an acid mixture. The acid mixture consists of 70%abletic acid and the remainder, a mixture of oleic and. linoleic acids.

2 Acetate salt of a diamine made by condensing acrilonitrile with aprimary amine made from tallow.

This process is especially applicable tov-the preparation of the2-alkyl-1,5-hexadiene-3-ynes in which the alkyl I 3 j group has from lto 5 carbon atoms. Although the process will be described in greaterdetail using as initial reactants, vinyl acetylene and acetone, otherketones such as methyl ethyl ketone or methyl vinyl ketone aswell asaldehydes may also be employed. In addition, other alkyl olefinicacetylenic hydrocarbons can be prepared lby starting with otheracetylenic compounds suc'has methyl acetylene, or diacetylene, andcondensing with the appropriate ketone. It is desirable but notessential to use ketones since the dehydration step-of the over-allprocess is Well adapted to the dehydration of the tertiary alcoholsproduced by the condensation of ketone type compounds.

When employing reactants and materials of a hazardous nature such asacetylene and especially some of the more reactive hydrocarbons whichhave additional doub1e and triple bonds, it is obvious that a continuousprocess possesses substantial advantages. The amount of materialshandled at any one time can be kept small enough so that in the event ofan explosion or other mishap, no extensive damage will result.Furthermore, the operating organic phase and anA aqueous phase and eachis collected of the reaction volume is in the recirculating section and80% is in the non-recirculating section.

The resulting reaction mixture from the condensation reaction vessel isthen brought into contact with water in order to hydrolize the potassiumsalt of the acetylenic alcohol which is produced. Both the aqueous andorganic phases are contacted in`a Vtower-which is provided with means tosecure intimatemixing, as for example, a perforated plate column.Contact in'this column is preferably countercurrent. The overhead orupper fraction from the hydrolysis column is then separated into anseparately. The acetylenic alcoholfrom the condensation is contained inthe xylene layer from which it may be separated by distillation, ifdesiredf" Depending on the boiling point of the alcohol produced Y bythe condensation, other hydrocarbons than xylene may y be employed asdiluents in the reaction in order to faciliconditions can becontinuously and carefully regulated to avoid substantially completelyundesirable polymerization reactions, while at the same time maintainingconditions for optimum yields of the desired condensation products. Infact, substantial commercial production of materials of this chemicaltype is practically impossible unless continuous production can besuccessfully employed.

The general process of the invention may be described as follows,allowing for suitable variations in the operation. A slurry of potassiumhydroxide in xylene is first made up in an agitated reactor vessel usingthe special and highly advantageous procedure which is further describedherein below.

With regard to making the slurry of potassium hydroxide, the temperatureemployed at atmospheric pres- Vsure can vary from about 140 C.(approximately the portion of xylene is employed. The concentrations ofY.

fatty acid, for example, oleic acid, which may be employed vary fromabout 1/2 to 5% by weight, with the preferred amount being about 1% byweight. Higher concentrations are to be avoided because a'very viscousslurry results. The preferred proportions of potassium hydroxide indiluent is approximately one part by weight of potassium hydroxide pertwo parts by weight of xylene. Concentrations as high as 1 to 1 havebeen employed but such proportions yield more concentrated slurrieswhich are more difiicult to handle and pump in the equipment.

A solution of an appropriate acetylenic hydrocarbon (vinyl acetylene)mixed with an appropriate carbonyl compound such as an aldehyde orketone (acetone) is kept in storage in a separate feed tank. The slurryof potassium hydroxide and the mixture of acetylenic hydrocarbon andcarbonyl compound are fed into the recirculating portion of acondensation reaction system'at different points. If desired, it is alsofeasible and possible to feed the acetylenic hydrocarbonreactant andthe'carbonyl compound reactant separately into the condensation system.Thus, there may be provided a first recirculating system in which theacetyleniohydrocarbon is reacted with the slurry of potassium hydroxide,and a second recirculating system into' which the resulting potassiumacetylide slurry is mixed with-the aldehydeor ketone. This mixtureY iscontinuouslypassed through jaV reactor in which the condensationreaction occurs. ,The .condensation vessel must provide the holdupvolume Vnecessary to allow the particular condensation reaction-toproceed to completion. densation reactor is such that it allows areaction time 0f between 1 5 minutes and 1 hour. Thus, apprQXimtely tateseparation of the product by distillation if this is desirable. In somecases, asrwhen further employing the alcohol as a chemical intermediate,it is preferable not to separate it from the diluent hydrocarbonin whichit was produced.

On the other hand, the hydrocarbon-alcohol layer can bemixed with asolution of suitably controlled dilute sulfuric acid and this mixture isagain continuously passed through a dehydrating zone such as a countercurrent contacting column at an elevated, controlled temperature duringwhich period the alcohol from the condensation is dehydrated to thehydrocarbon. The'mixture leaving this zone separates into two layers, anaqueous layer and a hydrocarbon layer. The hydrocarbon layer is thenpreferably subjected to a fractional distillation for the removal of thedesired acetylenic olenic hydrocarbon (2-methyl-1,5-hexadiene-3-yne)preferably as an overhead'product. Y

' The choice of operating temperatures is' not only governed bytheproperties of the postassium hydroxide slurry but also by the particularcondensation reaction which it is desired to carry out. Higher reactiontemperatures further the condensation reaction, but also favorpolymerization of the acetylenic hydrocarbonV reactants. Thesehydrocarbons varyV a great deal in degree of stability. For example, thecondensation of acetone and vinyl acetylene can be conducted effectivelyat temperatures ranging from 20 to 40 C. without excessive side reactionpolymerizations. Condensations involving such hydrocarbons asdiacetylene canbest be effected at 0 to 10 C. or lower. The normallygaseous acetylenic hydrocarbons such as acetylene or methyl acetylenerequire slight'modications of the continuous procedure. Methyl acetyleneis quite stable at high temperatures so that the preferred operation isat 20 to 30 C. Ywith suicient prescorresponding potassium acetylide,which then in'turn Preferably, the total volume of the con- Y isreactedV withthe desired ketone or aldehyde. Since aldehydes aregenerally more sensitive to elevated temperaturesvthan are ketones,lower temperatures are usually Nto be'preferred in condensationreactions involving aldehydes as reactants.

A number of unique and inventive features are embodied in thiscontinuous method of operation. The con-V tinuous condensation of theacetylene compound and the carbonyl compoundV in the presence of thepotassium hydroxide slurry is possible because of the discovery that thereaction takes `place relatively rapidly under these conditions. Theemployment of a continuous reactor system has the advantage that theYhazards usually asso- Vciatedwith handling large quantities of theexplosive and dangerous acetylenic compoundsare much reduced andeliminated. The immediate and'direct continuous dehydration of theacetylene condensation product with controlled amounts of sulfuric acidalso has the advantage of minimizing the hold-up Vof unstable materialand thereby avoiding substantial losses in yield of desired material. Itis further highly desirable to eect condensation, and if desired, thedehydration of the resulting alcohol condensation product, in thepresence of a relatively high boiling hydrocarbon diluent. The diluentshould be selected such that it does not interfere with the entirecondensation and dehydration reactions. The preferred hydrocarbondiluent for this purpose is xylene. The xylene which may be used can beeither one of the pure isomers or a mixture of two or more of theisomers such as is readily available commercially. The employment of adiluent such as xylene throughout the process has the advantage ofmaintaining a solvent in the presence of the usually unstable acetylenicpolymers, which otherwise are quite explosive and present hazards whenemployed in the pure state. In carrying out this continuous operation,the xylene concentration is maintained throughout the reactor, thedehydrator and in the iinal distillation steps during which elevatedstill temperatures may be experienced and would otherwise causeexcessive polymerization if the xylene were not present. This xylene orother suitable solvent may be recycled and reused throughout thecontinuous reactor system. If desired, the potassium hydroxide as wellas the acid dehydrating agent may also be recycled.

The following examples are intended to be for the Exampe 1 In a typicalspeciiic application of the above described process the preparation of2-methyl-5-hexene-3-yne-2-ol was carried out by the condensation ofacetone with vinyl acetylene.

The continuous condensation was carried out in an apparatus similar tothat described below and sketched in the accompanying schematic flowdiagram. A slurry of potassium hydroxide was made up in a blendingapparatus using 80 parts of potassium hydroxide, 160 parts of xylene andabout 2 parts of commercial oleic acid. The xylenepotassium hydroxidemixture was heated to about 140 C. (above the melting point of thepotassium hydroxide), and the oleic acid was added. The mixtureimmediately formed an emulsion which was agitated while undergoingcooling to 25 C. As the mixture cooled, the potassium hydroxidesolidiiied so that a suspensoid system consisting of` solid potassiumhydroxide particles suspended in xylene resulted. Using this procedure aslurry was obtained which was found to be entirely stable at roomtemperatures (with occasional slight agitation) for periods up toseveral months. The total volume of the reaction systemV employedincluding both the recirculating and non-recirculating portion. Theabove described slurry and vinyl acetylene-acetone mixture were each fedinto the system at a rate corresponding to 1 part by volume per minute.Equimolar quantities of vinyl acetylene and acetone (0.855 mole of each)were used. The recirculating portion of the system operated at 35 to 40C. and the non-recirculating portion was maintained at slightly aboveroom temperature at 25 C. The resulting reaction product was hydrolizedwithv 75 parts of concentrated sulfuric acid and there was obtained ayield of 2-methyl-5-hexene-3-yne-2-ol equivalent to 74% of thetheoretical quantity.

Example 2 A stable slurry of potassium hydroxide was made up in asimilar fashion as that described in Example l above, said slurrycomprising 80 parts of potassium hydroxide (1.43 moles), and 160 partsof Xylene and employing 2 parts of oleic acid as emulsifying agent. Intothis stable 6 suspension there was absorbed 0.924 mole (24 parts) ofacetylene by slowly passing acetylene into a recirculating systemcomprising 20 parts by volume. 'Ihe system was maintained at atemperature of approximately 35 to 40 C. Subsequently, this suspensionwas passed into a second recirculating system into which an equivalentquantity of 'butyraldehyde was introduced, that is, 0.92 mole. Followingthis introduction, the mixture was passed into a non-recirculatingchamber comprising 77 parts by volume. The resulting reaction productwas hydrolyzed to obtain a good yield of l-hexyne-S-ol.

Example 3 The following example will best be understood if it is read inconnection with the accompanying figure which is a schematic flow planpresented for the purpose of illustrating the process of the invention,although it is not intended to limit the invention specifically thereto.

The potassium hydroxide-xylene mixture is made up in vessel A which is areactor, the contents of which are continuously agitated by stirrer 2.The make up xylene is introduced into vessel A by line 1 andpelletedpotassium hydroxide is introduced by line 3. The slurry isprepared by continuously mixing the reactants at a ternperature of aboutC. with rapid agitation. After a suitable period of time, inreactorvessel A, the resulting finely divided `KOI-I-xylene slurry is passed byline 4 through inlet line 5 into the condensation reaction system B.This system consists of two sections, one recirculating and the othernon-recirculating. The KOH-xylene slurry is fed into the recirculatingsection of the reaction system; the circulation being maintained bymeans of pump 6. The acetylenic hydrocarbon (vinyl acetylene) and theketone (acetone) in the xylene diluent, are simultaneously introducedinto the recirculating section via line 7. The desired reactiontemperature (about 40 C.) is maintained by controlling the coolant ilowthrough an appropriate heat exchanger. The mixed reactants then passthrough the non-recirculating section 9 where the condensation reactionbetween the acetylenic hydrocarbon (vinyl acetylene) and the ketone(acetone) is allowed to go to completion. Any fixed gases in the systemare vented through trap 8.

The reaction mixture is then brought into contact with water which isfed throughV line 10. This water dissolves the unused KOH and alsohydrolyzes the potassium acetylide complexes. Complete hydrolysis isaccomplished by contacting the aqueous and organic phases in the packedhydrolysis column C. The total mixture is then passed (after hydrolysis)by line 12 into separator D.

The organic layer containing unreacted vinyl acetylene, xylene, anddesired condensation product passes via line 14 into dehydration reactorF. There is also introduced dilute sulfuric acid (about 30%) whichenters the system by line 1S. The aqueous layer from separator D issubsequently processed as described below. In dehydration reactor F, thecondensation product is subjected to an elevated temperature whereby itis continuously dehydrated to the acetylenic olen hydrocarbon. Thisdehyrated product passes by line 21 into phase separator H in which thegas phases which is principally unreacted acetylenic hydrocarbon isseparated and passed via recycle line 23 into line 5 and thence into thecondensation reaction system B. The organic layer obtained in separatorH is drawn olf by line 22 and thence is passed into an acid recoverysystem, if desired.

In-washer I, the organic layer containing the desired acetylenic olefinhydrocarbon product, undehydrated alcohol, and xylene is contacted withwater introduced by line 24. Wash water is removed yfrom the washer byline 25. The washed organic layer is then passed by line 26 intofractionating column I, wherein it is subjected to fractionaldistillation. Fractionating column I is preferably operated underreduced pressure. The desired hydrocarbon, 2methyl1,5-hexadiene-3-yne,is removed from this column by overhead line 33. VThis overhead streampasses through a condenser, A partof the condensed liquid is returned tothe column as reflux via line 34. The remainder is removed as product byline 3S. From the lower'portion of fractionation column I, a majorportion of the bottoms stream of undehydrated alcohol and Xylene isrecycled through line L20 into line 14 and thence into dehydrator F. Asmaller portion of the bottoms stream passes by line 27 into reruncolumn K. In this column, the xylene diluent is continuously purified byremoval of a polymer bottoms stream through line 28. The xylene isremoved overhead from column K by line 29 and passes through acondenser. A part is returned to column K by line 30 and the remainingportion passes through line 31 and is recycled backto the condensationand dehydration stages. Polymerization inhibitor can be added to thesystem by line 32, if desired.

The aqueous KOH layer containing some dissolved organic material ispassed through line '13 to extraction tower E, in which the layer iscontacted countercurrently with fresh Xylene introduced via line 17. Theenriched xylene is passed through lines 16 and 20 and thence into line14 to the dehydration reactor F. The stripped aqueous KOH solution ispassed to vaporizrer F in which Water' is removed by azeotropicdistillation with xylene to obtain anhydrous KOH which is removed by.line 19 and which can be used in making up the initial slurry in VesselA.

References Cited in the le of thisvpatent UNITED STATES PATENTS2,250,558 VVaughn July 29, 1941 2,385,546 Smith Sept. 25, 1945 2,394,608Hansley V Feb. 12, 1946 2,455,677 Horeczy Dec. 7, 1948 2,460,969 BlinoFeb.-8, 1949 2,579,257 Hansley et al. Dec. 18.r 1951 2,593,009 Clark etal. .Apr. 15, 1952 2,596,175 Rosenstein May 13, 1952 2,737,499 GrubbMar. 6, 1956 2,742,517 1956 Fusco Apr. 17,

OTHER REFERENCES Johnson: Acetylenic Compounds, vol. 1, pages 3-21(1946), Arnold & Co., London. Y

